The present invention relates to a modified polyolefin resin with improved adherence onto the surface of substrate, in particular, surface of substrate having nonpolar thermoplastic resin as a prime material and improved solubility into nonaromatic nonpolar solvent, its composition and uses.
Utilizing the nature to be transformed by heat, the thermoplastic resins are used as various configurations of commodities by molding into not only planar shapes such as sheets and films, but also certain shapes of spherical, cylindrical, box-like, etc. However, since the thermoplastic resins are fundamentally transparent, relatively soft and fragile, printing and painting are provided on their surfaces, for the purpose of improved protection and beautiful ornament.
The thermoplastic resins include resins with polarity and those with nonpolarity. Among nonpolar resins, polyolefinic resins such as polypropylene and polyethylene are adopted widely in recent years, because of low price and many excellent properties such as moldability, chemical resistance, water resistance, electrical characteristics and safety. Different from polar resins such as acrylic resin and polyester resin, however, the polyolefinic resin is nonpolar and crystalline, hence it is difficult to adhere ink, paint or adhesive firmly onto its surface.
In opposition to such substrates of nonpolar resins using polyolefinic resins, as resins with adherence, acid-modified polyolefin resins, from unsaturated carboxylic acid modification down, are proposed. The acid-modified polyolefin resin has adherence onto the nonpolar substrates, but its adherent strength is low and the coated film after drying has tack. For example, when acid-modified polyolefin resin is coated onto the surface of film-shaped substrate and dried to form film and then it is wound up, problems of clinging of dirts onto the surface of film and blocking after winding could not be avoided.
Moreover, the acid-modified polyolefin resin is generally poor in the solubility into solvent and the compatibility with other different types of resins, hence, usable solvents and mixable other resins were restricted on manufacturing paint for painting and printing ink, resulting in problems of difficult production of paint, ink, adhesive or the like with sufficient performance.
Moreover, in recent years, from the viewpoint of environmental problems, such resin that dissolves into solvents containing no aromatic solvent at all has been explored. However, with respect to the solvents to be used for dissolving conventional acid-modified polyolefin, the use of aromatic solvents such as toluene and xylene is essential, hence it was very difficult to dissolve into nonaromatic solvents while maintaining various physical properties such as adherence by the conventional techniques of acid-modified polyolefin.
As the means to improve the problems of solubility into solvent, compatibility with other resins, tack of dried film, and the like, a method of graft copolymerizing two or more unsaturated carboxylic acids or their derivatives with different properties onto polyolefin resin, as using unsaturated carboxylic anhydrides and nonanhydrides such as maleic anhydride and acrylic acid in combination, is disclosed in Japanese Unexamined Patent Publication Nos. Hei 9-40724, Hei 7-82328, Hei 3-227341, Hei 2-245042, etc. Moreover, in addition to the method of simple graft polymerization, a method of modification by further reacting polyester, alcohol, etc., after graft copolymerized unsaturated carboxylic acids or their derivatives such as acrylic acid and maleic anhydride onto polyolefin, is proposed in Japanese Unexamined Patent Publication No. Hei 11-217537. It is reported that the modified polyolefin resin obtainable by this method can improve the solubility into solvent, stability of solution on storing for a long term, etc.
However, when graft copolymerizing monomers of unsaturated carboxylic acids or their anhydrides such as acrylic acid and maleic acid onto polyolefin resin, in particular, polyolefin resin with high propylene content, it is known that the degradation (decrease in molecular weight) is accompanied [Journal of Polymer Science 33, 829 (1995) etc.]. With the modified polyolefin resin obtainable by modifying polyolefin resin with high propylene content by said method, decreased molecular weight was brought about, adherent strength onto nonpolar substrates was still insufficient, and also the problem of tack of formed film could not be solved.
On the other hand, it is also well known that, through the alteration of reaction conditions such as increased use level of said modifying monomer, increased molecular weight of grafting portion can be accomplished easily. In this case, however, the solubility into nonaromatic solvent improved, but sufficient adherent strength onto hard-adherent nonpolar substrates could not still be achieved, because of relative decrease in the content of polyolefin being a major component for developing adherent strength.
Moreover, when graft copolymerizing (meth)acrylic acid or its lower alkyl ester with relatively high polarity, homopolymer and copolymer ungrafting onto polyolefin skeleton were produced in large quantities, resulting in decreased solvent solubility and decreased solvent resistance of dried film etc., which did not come to the practical use.
As described, with the modified polyolefin resins obtained by conventional methods, the enhancement of adherent strength onto nonpolar resins was insufficient. In particular, onto the high-crystalline hard-adherent polyolefin moldings and untreated polyolefin resins without surface treatment for improved adherence such as corona treatment, the adherent strength was insufficient even in the case of reinforced adhesive conditions, hence more improvement in the adherent strength has been desired.
There, the purpose of the invention is to obtain a resin with excellent adherence even onto nonpolar substrates, in particular, hard-adherent nonpolar substrates without preliminary surface treatment for improving hard-adherence or adherence. Furthermore, it is to provide a resin that combines attributes of excellent solubility into nonaromatic solvent, good compatibility with other resins, and improved tack of films obtainable by coating and drying this resin itself or compositions such as paint and ink containing this resin as well.
As a result of diligent investigations, the inventors have found that, by combinationally using unsaturated polycarboxylic acid or its derivative and a particular (meth)acrylic ester as monomers for polyolefin resin and graft copolymerizing to modify, not only said problems are solved with use level of monomers of the order of not injuring the adherent strength, but also excellent adherent strength is exhibited even onto hard-adherent polyolefin moldings and untreated films of polyethylene and polypropylene under broad conditions from condition for adhesive treatment at high temperature to condition for adhesive treatment at low temperature of around room temperature to 100xc2x0 C. Furthermore, in this case, the inventors have found that the modified resin has excellent solubility into nonaromatic solvent as well as aromatic solvent, leading to the invention.
Namely, the invention relates to
(1) a modified polyolefin resin with polyolefin resin graft modified with unsaturated polycarboxylic acid or its derivative (A) and (meth)acrylic ester (B) represented by a following general formula, with contents of (A) and (B) of 0.1 to 20% by weight and 0.1 to 30% by weight, respectively, in modified polyolefin resin, and with weight average molecular weight of 15,000 to 150,000,
CH2xe2x95x90CR1COOR2xe2x80x83xe2x80x83(Chemical formula 2)
xe2x80x83(wherein R1=H or CH3, R2=CnH2n+1, n=integer of 8 to 18)
(2) the modified polyolefin resin of (1), wherein said unsaturated polycarboxylic acid or its derivative (A) is itaconic anhydride and/or maleic anhydride,
(3) the modified polyolefin resin of (1) or (2), wherein said (meth)acrylic ester (B) is at least one kind selected from octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate and stearyl (meth)acrylate,
(4) the modified polyolefin resin of any of (1) through (3), wherein said polyolefin resin is at least one kind selected from ethylene-propylene copolymer, propylene-butene copolymer, and ethylene-propylene-butene copolymer,
(5) a modified polyolefin resin composition characterized by formulating curing agent selected from epoxy, polyisocyanate, polyol, polyamine and curing agents with those functional groups blocked with protective group, to the modified polyolefin resin of any of (1) through (4),
(6) an adhesive containing modified polyolefin resin of any of (1) through (4) or modified polyolefin resin composition of (5),
(7) a primer containing modified polyolefin resin of any of (1) through (4) or modified polyolefin resin composition of (5),
(8) a paint containing modified polyolefin resin of any of (1) through (4) or modified polyolefin resin composition of (5), and
(9) an ink containing modified polyolefin resin of any of (1) through (4) or modified polyolefin resin composition of (5). In following, the invention will be explained in detail.
The modified polyolefin resin of the invention is suitable for an adherend having thermoplastic resin, in particular, non-polar thermoplastic resin as a substrate. The nonpolar resins include polypropylene, polyethylene, ethylene-propylene copolymer, propylene-butene copolymer, ethylene-propylene-butene copolymer, terpene resin and styrene resin. The modified polyolefin resin of the invention is characterized in that the adherends having these nonpolar resins as substrates can be used, even if they may be hard-adherent ones not subject to the surface treatments with plasma, corona, etc. for improved adherence. As for the shape of adherends, it is possible to apply to any of shapes suitable for the use, from planar shapes such as sheets and films and spherical, cylindrical, box-like and other shapes down.
The polyolefin resin of the invention is composed of olefins with number of carbon atoms of not less than 2 to not more than 20, preferably not less than 2 to not more than 6 such as ethylene, propylene, butene, pentene, hexene, heptene, octene and 4-methyl-1-pentene, and, above all, xcex1-olefins with said number of carbon atoms are preferable. Moreover, homo- or co-polymers of chain or cyclic polyenes such as cyclopentene, cyclohexene, 1,4-hexadiene, 1,5-hexadiene, divinylbenzene, 1,3-cyclopentadiene, 1,3-cyclohexadiene and 5-vinyl-2-norbornene, or styrene, substituted styrene, etc. can be used as the polyolefin resins of the invention. The proportion of these monomers in polymer can be selected arbitrarily, but, when hard-adherent nonpolar polyolefin resins such as crystalline polyethylene and polypropylene are adherends, the inventive modified polyolefin resins are preferable to be ethylene-propylene, propylene-butene and ethylene-propylene-butenecopolymer, and, in particular, the proportion of propylene in these resins is preferable to be not less than 50% to not more than 98%. If under 50%, then the adherence to adherend is poor, and, if over 98%, the flexibility is insufficient.
Upon producing the modified polyolefin resin of the invention, the molecular weight of polyolefin resin that becomes starting raw material is not particularly restricted. it is required, however, that the weight average molecular weight of modified polyolefin resin after modification becomes 15,000 to 150,000. When the molecular weight of raw material polyolefin resin is high, it is possible to adjust the molecular weight to a suitable range by degrading in the presence of heat or radical, or by degrading at the same time as modification reaction. Besides, the raw material polyolefin resins can be used solely or in combination of multiple kinds. Moreover, in the modified polyolefin resin of the invention, the raw material polyolefin is required to be not less than 50% by weight.
The unsaturated polycarboxylic acids or their derivatives (A) are unsaturated polycarboxylic acids such as maleic acid, fumaric acid, tetrahydrophthalic acid, itaconic acid, citraconic acid, crotonic acid, aconitic acid, phthalic acid, trimellitic acid and norbornenedicarboxylic acid, or their derivatives (e.g. acid anhyride, acid halide, amide, imide, ester, etc.). Thereamong, itaconic anhyride and maleic anhyride are preferable in the points of various physical properties of film of modified polyolefin resin, handling property and cost. The grafting weight of modifying component (A) in modified polyolefin resin is required to be 0.1 to 20% by weight, preferably 1 to 15% by weight and more preferably 2 to 10% by weight. If the grafting weight is lower than this range, then the solvent solubility and adherent strength onto substrates of modified polyolefin resin decrease. Also, if too high inversely, much unreacted materials generate, which is unpreferable. Besides, these modifying monomers (A) can be used solely or in combination of multiple kinds.
The (meth)acrylic ester (B) is at least one kind selected from compounds represented by a following general formula.
CH2xe2x95x90CR1COOR2xe2x80x83xe2x80x83(Chemical formula 3)
(wherein R1=H or CH3, R2=CnH2n+1, n=integer of 8 to 18)
Thereamong, octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate and stearyl (meth)acrylate are preferable in the points of various physical properties of film of modified polyolefin resin and cost. In the general formula shown above, if n is smaller than 8, the solvent solubility is aggravated, and, if n is larger than 18, then the tack is caused in film, which is unpreferable. Moreover, the grafting weight of modifying monomer (B) in modified polyolefin resin is 0.1 to 30% by weight, preferably 1 to 15% by weight. If the grafting weight is lower than this range, then the solvent solubility, compatibility with other resins and adherent strength onto substrates of modified polyolefin resin decrease. Also, if too high inversely, highly reactive modifying monomer (B) forms ultrahigh-molecular weight material to aggravate the solvent solubility likewise, or production level of homopolymer and co-polymer ungrafting onto polyolefin skeleton increases, which is unpreferable. Besides, these modifying monomers (B) can be used solely or in combination of multiple kinds.
Moreover, in the invention, depending on the use and purpose, monomers other than modifying monomers (A) and (B) can be used in combination within a range of not injuring the characteristics of the invention. The usable monomers are, for example, (meth)acrylic acid, (meth)acrylic acid derivative other than (B) (cyclohexyl (meth)acrylate, hydroxyethyl (meth)acrylate, benzyl (meth)acrylate, glycidyl (meth)acrylate, isocyanate-containing (meth)acrylate, etc.), and other copolymerizable unsaturated monomers such as styrene, cyclohexyl vinyl ether, and dicyclopentadiene. By using these monomers in combination, the adherence, solvent solubility, and grafting rate of modifying monomers (A) and (B) can be enhanced further. Besides, the use level of these monomers is preferable not to exceed the sum of grafting amounts of modifying monomers (A) and (B).
It is possible to conduct the graft reaction using said modifying monomers (A) and (B) and other modifying monomers, and to obtain the modified polyolefin resin by publicly known methods. For example, solution method wherein polyolefin resin is dissolved into solvent such as toluene under heating and modifying monomers are added, melt method wherein modifying monomers are added together with molten polyolefin resin employing Banbury mixer, kneader, extruder, etc., and the like are mentioned. The method of adding modifying monomers is not minded whether they are added one by one or added in a lump.
To the modified polyolefin resin of the invention, reaction aid for improving the grafting efficiency of unsaturated carboxylic acid, stabilizer for adjusting the stability of resin, radical initiator for promoting the reaction, and the like can be formulated additionally, depending on the purpose for use.
As the reaction aids, styrene, o-methylstyrene, p-methylstyrene, xcex1-methylstyrene, divinylbenzene, hexadiene, dicyclopentadiene, etc. are mentioned. As the stabilizers, hydroquinone, benzoquinone, nitrosophenylhydroxy compound, etc. can be mentioned. The radical initiator can be selected appropriately from publicly known products, but, for example, it is preferable to use organic peroxides such as benzoyl peroxide, dicumyl peroxide, lauroyl peroxide, di-t-butyl peroxide and cumene hydroperoxide.
The weight average molecular weight of modified polyolefin resin thus obtained is 15,000 to 150,000, preferably 30,000 to 120,000. Particularly preferable is 30,000 to 100,000. If under 15,000, then the adherent strength onto nonpolar substrates and the cohesive strength become poor, and, if over 150,000, the workability, solubility into solvent and compatibility with other resins decrease due to increased viscosity.
Besides, as the measuring methods of weight average molecular weight, GPC method and light scattering method are known, and the molecular weight in the invention is molecular weight determined by GPC method. The grafting weight % of modifying monomers (A) is determined by alkali titration method, but, in the case of imide etc. wherein the derivatives have no acidic group, it is determined by FT-IR method. Also, the grafting weight % of modifying monomers (B) is determined by FT-IR method.
Moreover, the invention relates to a modified polyolefin resin composition formulated with curing agent selected from epoxy, polyisocyanate, polyol and polyamine, or curing agent selected from ones with those functional groups blocked with protective group, to said modified polyolefin resin.
As the epoxy curing agents, 1,2,3,4-diepoxybutane, 1,2,7,8-diepoxyoctane, 1,2,9,10-diepoxydecane, vinylcyclohexene diepoxide, 1,2,5,6-diepoxycyclooctane, 3,4-epoxycyclohexylmethyl-3xe2x80x2,4xe2x80x2-epoxycyclohexanecarboxylate, 1,4-butanediol glycidyl ether, 1,6-hexanediol glycidyl ether, polyethyleneglycol glycidyl ether, polypropyleneglycol glycidyl ether, glycidyl hexahydrophthalate, glycidyl ester of dimeric acid, triglycidyl isocyanurate, tetraglycidyldiaminodiphenylmethane, etc. are mentioned.
As the polyisocyanate curing agents, polyisocyanate curing agents such as ethylenediisocyanate, propylenediisocyanate, tetramethylenediisocyanate, hexamethylenediisocyanate, m-phenylenediisocyanate, p-phenylenediisocyanate, 2,4-tolylenediisocyanate, 2,6-tolylenediisocyanate, 1,5-naphthylenediisocyanate, 4,4xe2x80x2, 4xe2x80x3-triphenylmethanetriisocyanate, 4,4xe2x80x2-diphenylmethanediisocyanate, m-xylylenediisocyanate, p-xylylenediisocyanate, isophoronediisocyanate and lysineisocyanate, polyisocyanate curing agents with two or more functionality obtainable by addition reaction or addition polymerization reaction of excess of said polyisocyanate curing agent with low-molecular polyol, for example, ethylene glycol, propylene glycol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, hexamethylene glycol, cyclohexanedimethanol, trimethylolpropane, glycerine, pentaerythritol or the like, polyisocyanate curing agents having Burette structure, polyisocyanate curing agents having allophanate structure, polyisocyanate curing agents having nurate structure, and curing agents with isocyanate groups of said polyisocyanate curing agents blocked with protective groups, called block isocyanates generally, are mentioned.
As the polyol curing agents, low-molecular polyol curing agents such as ethylene glycol, propylene glycol, neopentyl glycol, 2,2,4-trimethyl-1,3-pentanediol, hexamethylene glycol, cyclohexanedimethanol, trimethylolpropane, glycerine and pentaerythritol, polyethylene glycol, polypropylene glycol, polytetrahydrofuran, copolymer of ethylene oxide with propylene oxide, hydrogenated polybutadiene with hydroxyl group at end, polyesterpolyols obtainable from excess of said low-molecular polyols and dicarboxylic acids such as terephthalic acid, isophthalic acid, succinic acid, adipic acid, sebacic acid and hexahydroterephthalic acid, and the like are mentioned.
As the polyamine curing agents, diethylenetriamine, triethylenetetramine, isophoronediamine, N-aminoethylpiperazine, m-xylylenediamine, diaminodiphenylmethane, melamine, methylolated melamine, etc. are mentioned. Also, polyhydrazide compounds such as carbohydrazide, oxalic acid dihydrazide, succinic acid dihydrazide, glutamic acid dihydrazide, azelaic acid dihydrazide, undecanoic acid dihydrazide, maleic acid dihydrazide, itaconic acid dihydrazide and terephthalic acid dihydrazide can also be used similarly. Furthermore, curing agents with amino groups of said polyamine curing agents blocked with protective groups, called block amines generally, are also used.
The formulation level of said curing agents can be selected appropriately depending on the amount of functional groups (carboxyl group, acid anhydride group, hydroxyl group, etc.) in the modified polyolefin resin of the invention, but it is preferable to formulate so as the proportion of the number of said functional groups in the modified polyolefin resin that take part in the reaction to the number of functional groups (e.g. numbers of isocyanate groups, hydroxyl groups and amino groups) to become 10:1 to 1:5. In particular, a range from 5:1 to 1:2 is preferable in the points of various physical properties of film, in particular, adherence and gasohol resistance. If the formulation level of curing agent is higher than this range, the adherence decreases and, if too low, desired physical properties such as adherence, solvent resistance and water resistance cannot be obtained. Moreover, when formulating the curing agent, catalysts such as tin-based compounds can also be used in combination depending on the purpose.
The modified polyolefin resin of the invention can be used by itself or as a component for providing adherence in a variety of uses such as adhesive, primer, paint and ink, and can be used in the forms adapted to uses such as solution, powder, paste and sheet. Moreover, at that time, additives, for example, antioxidant, light stabilizer, ultraviolet absorber, pigment, dye, inorganic filler, etc. can be formulated, if need be. When using as a solution, aromatic solvents such as toluene and xylene, aliphatic solvents such as cyclohexane, methylcyclohexane, ethylcyclohexane, heptane, nonane and decane, ester solvents such as ethyl acetate and butyl acetate, ketonic solvents such as acetone, methyl ethyl ketone and methyl butyl ketone, alcoholic solvents such as methanol, ethanol, propanol and butanol, or mixtures of said solvents can be used, but, in view of the environmental problem, it is desirable not to use aromatic solvents. In particular, use of mixtures of cyclohexane-based aliphatic solvents with ester or ketonic solvents is preferable.
As the conditions of heat treatment when using the modified polyolefin resin of the invention, it is laminated onto film at a high temperature of around 170 to 180xc2x0 C., or, after coating by spraying, brush coating, bar coating or the like in the state of solution, it is dried or baked at a temperature of around 80 to 100xc2x0 C., or only dried at room temperature as it is for use.
When using as an adhesive or ink, not only nonpolar substrates such as polyethylene and polypropylene, but also polar substrates such as polyester, polyurethane, polyamide and aluminum are used very often in combination. Since the inventive modified polyolefin resin also has the adherence onto such polar substrates, it is suitable also for said use.
Also, when using as a primer or paint, the inventive modified polyolefin resin is excellent in the adherence to upper paint and clear coating, hence it is suitable for both polar substrates and nonpolar substrates.
When using as a paint or ink, other resins such as urethane resin, epoxy resin, acrylic resin, phenol resin, alkyd resin, polyamide resin, polyimide resin, silicone resin and nitrocellulose, being different types from polyolefin resin, may be blended, if need be.
In these uses, when blending the inventive modified polyolefin resin with said additives and other different types of resins, it is required to formulate the inventive modified polyolefin resin in amounts of at least 5% by weight or more, specifically 30% by weight or more by solids based on overall resin weight to maintain the adherence onto nonpolar or polar substrates.
Best Embodiment to Put the Invention into Practice
In following, the invention will be illustrated in more detail based on examples, but the invention is not confined thereto. Besides, the molecular weight was determined under the conditions of 40xc2x0 C. and 1 ml/min, making tetrahydrofuran as a developing solvent and using RI as a detector.